1. Field of the Invention
The present invention relates to resilient, reusable gaskets, and particularly to gaskets for use in sensitive equipment such as computer disk drives.
2. Description of Related Art
Gaskets formed from expanded polytetrafluoroethylene (PTFE) are widely employed today. These gaskets, typically made in accordance with the teachings of U.S. Pat. No. 3,953,566 issued Apr. 27, 1976, to Robert W. Gore, have a number of significant operating advantages, including cleanliness, high strength, chemical inertness, and high temperature resistance. Unfortunately, expanded PTFE material generally requires a significant amount of compression before achieving a proper seal. While the seal obtained with compressed expanded PTFE is a good one, repeat access through a sealed joint is limited. Like many other available gasket materials, once expanded PTFE gaskets are used they are permanently densified and have limited ability to be reused.
For use in sensitive electronic and optical enclosures, an expanded PTFE gasket is primarily of benefit due to its cleanliness. However, the need to repeatedly access some of these enclosures, and the substantial amount of densification required to properly seal some expanded PTFE materials, are significant concerns about using conventional expanded PTFE gaskets in such environments.
In particular, one such application is in computer disk drives where a clean resilient gasket is desired. Cleanliness is required both from a particulation standpoint as well as an out-gassing standpoint because particles as well as hydrocarbons, plasticizers and silicone out-gassing are problematic in operating the disk drive. Unfortunately, auguring against using expanded PTFE material, disk drives are typically sealed with only a few small screws so sealing force is severely limited.
The most common gaskets used in disk drives today are molded rubber or VITON gaskets, or closed cell polyolefin form gaskets. These gaskets have the benefits of being fairly inexpensive and not presenting a contamination risk by having limited "out-gassing." Regretfully, these gaskets typically have many deficiencies, such as: being difficult to handle, having limited reusability, and having limited sealability (with leaking of air occurring around some gaskets in certain applications). Additionally, in certain applications which are highly sensitive to contamination problems (e.g., in smaller and more complex disk drives), the amount of out-gassing which does occur with many of these gaskets is becoming an increasing concern.
What has not been available is a gasket that is a resilient, clean-polymeric gasket that is easily applied, easily removed, and easily reapplied with the stability required to make a good gasket seal. Additionally, it would be desirable to have a gasket with a number of other properties, such as: sufficient porosity to provide particle filtration capability as an air filter when installed; a gasket material which can be optionally loaded with an adsorbent or other reagent; a gasket which includes certain electromagnetic and/or thermal conducting or shielding properties; and a gasket which can protect against liquid contamination.
These and other purposes of the present invention will become evident from review of the following specification.